The invention relates generally to brake systems for railroad cars, and more particularly to improvements in a truck mounted brake system wherein a brake cylinder is mounted on a truck bolster.
In brake systems of the type to which the present invention relates, the brake cylinder is attached to a first sidewall of the bolster by two bolts or studs extending through holes in the bolster. A cylinder rod extends through the bolster and is connected to a lever on the opposite side of the bolster.
While braking systems of this type have proven satisfactory in operation, the installation of the brake cylinder has generally been a difficult and time consuming task, both in the context of new installations and in the context of replacing the brake cylinder after a period of use. Originally, brake cylinders of this type were manufactured with threaded bores to receive bolts extending through holes from the bolster interior. It was necessary for the brake cylinder, which weighs about 30 pounds, to be supported in its proper position, with its threaded bores aligned with the bolt holes in the bolster, while the bolts were inserted into the threaded bolt holes in the brake cylinder and tightened. Tightening of the bolts required maneuvering a wrench in a confined and difficult location within the bolster interior.
In an effort to alleviate the difficulty in installation, some brake cylinders were manufactured with studs pre-installed thereon for insertion through the bolster bolt holes, thus only requiring that nuts be placed on the threaded studs after their insertion into the bolster. However, placement of the nuts on the threaded studs and tightening of the nuts has still required maneuvering a wrench in an awkward location, and has still been a difficult and time consuming task. Thus, installation of the brake cylinder has remained a difficult and arduous task that may require two workers.
Because the bolster is a heavy iron or steel casting which must be capable of supporting loads on the order of 100 tons, its geometry cannot be altered to facilitate access to the bolt heads or nuts without consideration of possibly detrimental effects on its load capacity, durability, and wear life. Any alteration of the bolster or brake system configuration must also take into account clearances needed for pivoting of the truck and for avoidance of interference with the placement and operation of other equipment.
In the past, efforts to facilitate access to the bolt heads or nuts involved use of specially-designed torque wrenches with a plurality of joints and specially-ground custom sockets. However, it has been found to be difficult or impossible to accurately measure torque with these devices. It is important that the bolts or nuts be tightened to an appropriate torque, because otherwise the bolts or nuts may loosen over time, after being subjected to the dynamic loads and vibrations associated with use of the railroad cars and their braking systems for an extended period. Thus, the difficulty in measuring torque accurately has been problematic.
Even where the nuts or bolts are properly torqued, they may loosen over time. It is an object of the invention to facilitate accurate measurement of bolt or nut torque in this context and to address the problem of loosening of the subject bolts and nuts during use.
A further problem addressed by the invention relates to increasing the life of the brake cylinders. The cylinder rod is typically guided by a bushing at the location where the piston rod protrudes from the cylinder. In the past, the geometry of the brake system was such that the pivot point at which the brake cylinder rod engaged the brake lever was aligned coaxially with the axis of the bushing when the piston rod was in its retracted position, in which the brakes were not applied. When the brake cylinder rod is shifted to its extended position in this type of prior art system, the pivot point moves arcuately and accordingly moves off axis by about 1/4 in., which tends to misalign the piston rod slightly and leads to wear on the bushing, particularly because when the piston rod is extended, the brakes are applied, and accordingly the piston rod is under load.
It is a general object of the invention to provide an improved truck mounted braking system to facilitate installation and to increase reliability and useful life. Further objects of the invention will become apparent from the detailed description set forth below and the accompanying drawings.